This invention relates to a method of molding an optical element in which a resin layer is integrally molded on the surface of a glass member.
In the prior art, a method is known in which a thin film comprising a resin material is molded on the surface of a glass member to form a lens having an aspherical shape, which is difficult to work when the material is glass. The lens molded by this method generally is referred to as a replica lens.
As shown in FIG. 1, the method of molding a replica lens in the prior art includes placing a glass member 50, which has been worked into a spherical shape having a curvature approximating a desired aspherical shape, upon a molding member 52 having a molding surface 52a of the desired aspherical shape, filling a space 54 between a surface 50a of the glass member 50 and the molding surface 52a of the mold member 52 with a liquified resin and causing the resin to harden, thereby forming a replica lens 55 having the desired aspherical shape.
In a molding method of this kind, it is required that the molding surface 52a of the mold member 52 be supplied with the resin material in advance before the glass member 50 is placed upon the mold member 52. As one method of supplying the resin material, the resin material is dropped upon the molding surface 52a from a tip 60a of an apparatus for supplying the resin material, as shown in FIG. 2, with the tip 60 being kept spaced away from the molding surface. In an alternative method, as depicted in FIG. 3, the tip 60a of the supply apparatus 60 is brought in close proximity to the molding surface 52a, under which condition the resin material is supplied to the molding surface.
However, both of these supply methods involve problems. Specifically, with the method in which the resin material is dropped onto the molding surface 52a while the tip 60a of the supply apparatus 60 is kept spaced away from the molding surface, as shown in FIG. 2, air bubbles become entrapped in the resin material owing to the shock sustained when the resin material drops. With the method in which the resin material is supplied while the tip 60 of the supply apparatus 60 is held close to the molding surface 52a, as shown in FIG. 3, the resin material attaches itself to the tip of the supply apparatus, as a result of which an accurate amount of the resin material cannot be supplied.
Further, in the process of placing the glass member 30 upon the support member 52 after the resin material has been supplied to the molding surface 52a, there is the danger that air bubbles will become entrapped in the resin material. If the resin hardens while containing such air bubbles, the entrapped air bubbles that can be confirmed visually render the manufactured product unsuitable for shipping even if the air bubbles are entrapped to a degree that will not affect the optical function of the lens. As a consequence, a problem which arises is a decline in the yield of the replica lens manufactured.